Brominated Styrenic Polymers and Their Preparation

ABSTRACT

Preparing brominated styrenic polymer by maintaining a mixture formed from (i) brominating agent, (ii) a solvent solution of styrenic polymer, and (iii) aluminum halide catalyst, at −20 to +20° C., and terminating bromination in 20 minutes or less. New brominated anionic styrenic polymers have better melt flow and/or lower initial ΔE values than the best previously-known brominated anionic styrenic polymers. Other features of such new polymers include high thermal stabilities at 320° C. and/or very low initial color values. Brominated styrenic polymers, especially brominated anionic styrenic polymers, are useful as flame retardants for thermoplastic polymers.

REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 11/453,542,filed Jun. 14, 2006, now allowed, which in turn claims the benefit andpriority of U.S. Provisional Application Nos. 60/696,468, filed Jun. 30,2005, and 60/790,431, filed Apr. 6, 2006, the disclosures of which areincorporated herein by reference.

TECHNICAL FIELD

This invention relates to brominated styrenic polymers with improvedmelt flow properties, such as improved melt flow and/or low colorvalues, their preparation, and their use.

BACKGROUND

Commonly-owned U.S. Pat. Nos. 5,677,390, 5,686,538, 5,767,203,5,852,131, 5,852,132, 5,916,978, 6,133,381, 6,207,765, 6,232,393,6,232,408, 6,235,831, 6,235,844, 6,326,439, and 6,521,714 describe whatis believed to be the best known prior process technology for producingbrominated styrenic polymers such as brominated polystyrene having thebest known properties of any previously-known brominated styrenicpolymer. In this connection, the terms “brominated styrenic polymer” and“brominated polystyrene” as used in the specification and in the claimshereof refer to a brominated polymer produced by bromination of apre-existing styrenic polymer such as polystyrene or a copolymer ofstyrene and at least one other vinyl aromatic monomer, as distinguishedfrom an oligomer or polymer produced by oligomerization orpolymerization of one or more brominated styrenic monomers, theproperties of the latter oligomers or polymers typically beingconsiderably different from brominated polystyrene in a number ofrespects.

Over the years considerable efforts have been made by various parties toimprove upon the properties of brominated styrenic polymers, such asimproved melt flow and/or low color values. Despite their best efforts,it appears that no party has been able to produce or provide abrominated styrenic polymer having the high melt flow values and/or lowcolor values, much less the combination of excellent properties, of thebrominated styrenic polymers producible and provided by this invention.Nor has a prior party found the processing relationships that makepossible the production of such improved brominated styrenic polymers.

BRIEF SUMMARY OF THE INVENTION

It has now been discovered, inter alia, that in the aluminum halidecatalyzed bromination of a styrenic polymer, reaction time has aprofound influence on the type of product formed. More specifically, ifthe bromination reaction mixture is formed and exists for a very shortperiod of time at a suitably low temperature and then the reaction ispromptly terminated, a brominated styrenic polymer is formed havingimproved melt flow and/or color properties as compared to productsproduced in a reaction mixture that exists for a longer period of time,such as during a feed period of 30 minutes and a cook period of 5minutes, the shortest residence times referred to in commonly-owned U.S.Pat. Nos. 6,113,381, 6,232,393, 6,232,408, 6,235,831, 6,235,844, and6,521,714. This is an unexpected result because there is nocorresponding change in molecular weight, and the respective productsshow very little difference in their excellent thermal stabilities (asexhibited for example by thermal HBr evolution at 320° C.) that couldotherwise influence melt flow (measured at 220-270° C.). The brominationprocess embodiments of this invention can be applied to bromination ofstyrenic polymers produced by free radical polymerization, by anionicpolymerization or by cationic polymerization, with use of styrenicpolymers produced by free radical polymerization being preferred and useof styrenic polymers produced by anionic polymerization being morepreferred.

The available experimental evidence indicates that in the aluminumhalide catalyzed bromination of styrenic polymers, short reaction timesresult in the formation of kinetic bromination products, whereas aproduct formed in a reaction mixture that exists for longer periods oftime is a thermodynamic product. Whatever the mechanism of thistransformation, the available evidence indicates that the differencebetween the respective products is a difference in chemical structure.On comparing NMR spectra, brominated styrenic polymers produced by thisinvention have more hydrogen atoms in the ortho ring positions than doproducts formed from the same components in processes conducted undercomparable reaction conditions, but involving longer feed times and useof cook periods. A plausible explanation for this difference is that byuse of short reaction times, much of the bromine tends to occupypositions other than the ortho position(s). For instance, the 2,4,6- and2,3,6-tribromo isomers are expected to be the least favored of the sixpossible tribromo isomers for products made with short reaction times,and the only tribromo having no ortho Br's 3,4,5-tribromo, may be mostfavored. High ortho bromination tends to introduce considerable stericstrain on the polymer backbone which in turn can result in more extendedchain conformations relative to the 3,4,5-tribromo isomer, for example.Such chain extension would increase melt viscosity thus causing theobserved decrease in melt flow for the isomers having greater orthobromination. Additional evidence in support of different brominationproducts being formed pursuant to this invention is a 2 to 10° C.decrease in glass transition temperature observed for products of thisinvention as compared to comparable products produced with longerreaction residence times.

Accordingly, one embodiment of this invention is a process of preparingbrominated styrenic polymer, preferably using styrenic polymer formed byfree radical polymerization, and more preferably by using styrenicpolymer produced by anionic polymerization, which process comprisesmaintaining a reaction mixture formed from (i) a brominating agent, (ii)a solution of such styrenic polymer in a solvent, and (iii) aluminumhalide catalyst in which the halogen atoms are bromine or chlorine withat least one such halogen atom being a bromine atom, at one or moretemperatures in the range of −20 to +20° C. so that bromination ofpolymer occurs, and terminating the bromination of polymer in suchreaction mixture in a bromination time of 20 minutes or less.

Another embodiment of this invention is a new brominated anionicstyrenic polymer having (i) a bromine content of at least about 66 or 67wt %, for example in the range of about 66-72 wt % and (ii) a highermelt flow index as compared to previously-known comparable brominatedanionic styrenic polymers, as measured using ASTM Test Method D1238-00.The term “previously-known comparable brominated anionic styrenicpolymers” is defined hereinafter. Although it is possible and within thescope of this invention to produce brominated styrenic polymers having72 wt % of bromine, it is difficult to do so, and therefore the newbrominated anionic styrenic polymers of this embodiment will usuallyhave a bromine content of at least about 66 wt % but less than 72 wt %,e.g., in the range of about 66-71 wt %. More preferably these and othernew brominated anionic styrenic polymers of this invention have brominecontents in the range of about 67-70 wt %.

Still another embodiment of this invention is brominated anionicstyrenic polymer wherein said polymer has a bromine content of at leastabout 66 or 67 wt %, for example in the range of about 66-72 wt % andwherein said polymer is one in which the percentage of aromatic ringshaving ortho bromine atoms thereon as measured by proton NMR is lessthan the percentage of the aromatic rings having ortho bromine atomsthereon in previously-known comparable brominated anionic styrenicpolymers. For the same reasons as given above, these new brominatedanionic styrenic polymers of this embodiment will usually have a brominecontent of at least about 66 wt % but less than about 72 wt %, e.g., inthe range of about 66-71 wt %. More preferably these new brominatedanionic styrenic polymers of this embodiment have bromine contents inthe range of about 67-70 wt %.

In addition to superior melt flow characteristics the novel brominatedanionic styrenic polymers of this invention have other desirableproperties. For example, a brominated anionic polystyrene of thisinvention was found to have an unusually low initial color (ΔE=0.18) andexcellent thermal stability (59 ppm HBr) as measured by the 320° C.Thermal Stability Test. Also, high bromine levels (e.g., 70 wt %bromine) can be obtained using process technology of this invention inreaction times as short as 8 minutes.

Apart from superior melt flow properties, this invention can alsoprovide anionic styrenic polymers having extremely low initial HunterSolution ΔE values, and preferably one or more additional highlydesirable properties as well. As used herein, including the claims, theterm “anionic styrenic polymer” or “anionic polystyrene” denotes thatthe polymer referred to has been produced by use of an anionicpolymerization initiator, such as a lithium alkyl.

Accordingly another embodiment of this invention is brominated anionicstyrenic polymer wherein said polymer has an initial Hunter Solution ΔEvalue in the range of above zero to 1.50, preferably in the range of0.15 to 1.40, and even more preferably in the range of 0.18 to 1.32.Preferably, these brominated anionic styrenic polymers also have (1) aGPC weight average molecular weight (Mw) in the range of about 8,000 toabout 50,000 (preferably in the range of about 10,000 to about 30,000),and more preferably in the range of about 10,000 to about 20,000; or (2)a thermal stability in the 320° C. Thermal Stability Test of 150 ppm ofHBr or less (preferably 120 ppm of HBr or less); or (3) a brominecontent of at least about 66 or 67 wt %, for example in the range ofabout 66-72 wt %, and as explained above, usually less than about 72 wt%, e.g., in the range of about 66-71 wt %, and more preferably in therange of about 67-70 wt %; or (4) a combination of any two, or allthree, of (1), (2), (3).

Other features and embodiments of this invention will be still furtherapparent from the ensuing description and appended claims.

FURTHER DETAILED DESCRIPTION OF THE INVENTION Process Technology

One embodiment of this invention is a process of preparing brominatedstyrenic polymer which can be conducted as a batch or semi-batchprocess, or as a continuous process. This process comprises maintaininga reaction mixture formed from (i) a brominating agent, (ii) a solutionof styrenic polymer in a solvent, and (iii) aluminum halide catalyst inwhich each halogen atom is a chlorine or bromine atom with an average ofat least one such halogen atom per molecule being a bromine atom, at oneor more temperatures in the range of −20 to +20° C. so that brominationof polymer occurs, and terminating the bromination of polymer in suchreaction mixture in a bromination time of 20 minutes or less, preferably10 minutes or less, and more preferably 5 minutes or less. Usually theminimum bromination time is approximately 1 minute. In this connection,bromination time is time during which bromination can occur. Forexample, if, say, a continuous feed of (ii) is initiated followed 1minute later by initiation of a continuous feed of (iii), followed 1minute later by initiation of a continuous feed of (i), the brominationtime starts with the initiation of the feed of (i) because in the priortwo minutes bromination would not occur. In a more particular embodimentof this process, the brominating agent is bromine. It is preferred thatat least 50 wt % of the styrenic polymer, more preferably at least 80 wt% of the styrenic polymer, used in forming the solution of styrenicpolymer of (ii) above is polystyrene. Even more preferably polystyreneitself is used in forming the solution of (ii) above.

Components (i) and (ii) can be proportioned to produce brominatedstyrenic polymers containing any suitable quantity of bromine, whichtypically will be in the range from at least about 50 wt % up to amaximum of about 72 wt %. Thus, brominated styrenic polymers that can beproduced by a process of this invention typically contain at least about50 wt %, preferably at least about 60 wt %, more preferably at leastabout 67 wt %, and still more preferably in the range of about 68 toabout 72 wt % of bromine. The manner of proportioning the styrenicpolymer and the brominating agent to achieve various desired brominecontents are known to those of ordinary skill in this art and have beendescribed in the commonly-owned patents referred to at the outset ofthis document. Thus anyone unfamiliar with the art desiring furtherdetails should consult the commonly-owned patents referred to at theoutset. One of the highly advantageous features of this invention isthat the process technology of this invention provides significantlyimproved properties in brominated anionic polystyrenes, even in the caseof those having a bromine content as high as about 70 wt % or above.

There are various ways in which the processes of this invention can becarried out. One such method, which may be termed a batch or asemi-batch mode of operation involves rapidly introducing components(i), (ii), and (iii) into a reactor such as a stirred pot reactor sothat the maximum time that any portion of the components are undergoinga bromination reaction does not exceed about 20 minutes. At about 20minutes or less, the mixture in the stirred pot reactor is rapidlyquenched either by introduction of a quenching composition into thereactor or by dumping the contents of the reactor into a quenchingvessel containing the quenching composition. In this way, no portion ofthe reaction mixture undergoes bromination for more than about 20minutes. So that the last portion of components fed to the reactor havesufficient time to undergo suitable bromination, it is desirable to stopthe feeds and to allow a period of at least 1-2 minutes beforeterminating the bromination at or within the overall time of about 20minutes or less from the initiation of the feeds of at least components(i), (ii), and (iii), to serve as a residual period of at least 1 to 2minutes for the last portion of the components to undergo bromination.This batch or semi-batch mode of operation should involve rapidintroduction of the components into the reactor and also sufficientlyrapid agitation and efficient cooling of the reactor contents so thatthe reaction temperature is maintained within the above-specifiedtemperature ranges and within a suitable bromination reaction time of nomore than about 20 minutes.

A preferred mode of operation pursuant to this invention involves use ofa continuous process. In one such preferred embodiment of thisinvention, there is provided a process of preparing brominated styrenicpolymer, which process comprises:

-   A) causing reaction mixture continuously formed from components    comprised of (i) a brominating agent, (ii) a solution of styrenic    polymer in a solvent, and (iii) aluminum halide catalyst in which    the halogen atoms are bromine or chlorine atoms and in which at    least one such atom is a bromine atom, to continuously travel    through and exit from a reaction zone maintained at one or more    temperatures in the range of −20 to +20° C., and preferably in the    range of 1 to 10° C., so that bromination of polymer occurs during    at least a portion of such travel;-   B) terminating bromination of polymer in the reaction mixture as or    after reaction mixture exits from the reaction zone; and-   C) continuously having the time between formation of reaction    mixture in A) and termination in B) in the range of 1 to 20 minutes,    preferably in the range of 1 to 10 minutes, and more preferably in    the range of 1 to 5 minutes.    In conducting this continuous process, preferably the reaction    mixture as continuously formed in A) is comprised predominately or    entirely of a liquid mixture, preferably the brominating agent is    bromine, and preferably the bromine is continuously fed within the    confines of the liquid reaction mixture being continuously formed.    The term “confines” of course means within the body of the liquid    reaction mixture as distinguished from feeding onto an exterior    portion of the liquid reaction mixture. Feeding into the confines    can be accomplished by use of an injector or feeding probe which    extends into the body of the liquid reaction mixture being formed in    the reaction zone so that the bromine is forced into the liquid as    it leaves the injector or feeding probe. In a batch/semi-batch    operation in a stirred pot type of reaction vessel it is desirable    to position the exit portion of the injector or probe so that it is    in close proximity to the periphery of the stirring blades so that    the bromine is quickly dispersed within the body of the liquid    reaction mixture being formed in the reaction zone.

In the continuous mode of operation the reaction mixture formed in A)from components (i), (ii), and (iii) can be formed in various ways. Forexample, the bromination reaction mixture can be formed by feeding (i),(ii), and (iii) continuously but separately from each other, into thereaction zone. Another way of forming the bromination reaction mixtureinvolves feeding (ii) and a mixture of (i) and (iii) continuously intothe reaction zone, with the feed of (ii) being separate from the feed ofthe mixture of (i) and (iii). Still another way of forming thebromination reaction mixture is to feed a mixture of (ii) and (iii) anda separate feed of (i) continuously into the reaction zone. It will beappreciated that there can be plural feed inlets to the reaction zonefor one or more of (i), (ii), and (iii). Regardless of how many feedinlets are used and how the feeds are carried out (e.g., as threeseparate feeds or as two separate feeds, one of which is a combinationof (i) and (iii) or of (ii) and (iii) and the other is (ii) or (i),respectively), the feeds should be substantially concurrent (except atstart up when the feeds can be started at different times). Slight feedinterruptions which cause no substantial imbalance in the operation canbe tolerated but if possible, should be avoided or at least minimized sothat steady state operation may be achieved. While it is preferred thatall such feeds be continuous feeds, it is deemed possible to operatewith one or more pulsed feeds having uniformly short time intervalsbetween individual pulses. In each of the foregoing ways of carrying outthe feeds in A), a separate concurrent continuous or discontinuous feedof solvent can be utilized as another feed stream in A), if desired. Asin the case of the batch/semi-batch mode of operation, it is desirableto have the individual bromine feed(s) or the feedmixture(s)/solution(s) containing bromine to be fed directly into theconfines of the liquid reaction mixture being formed in the reactionzone so that the bromine is rapidly dispersed within such liquidreaction mixture as it is being formed. Thus the reaction zone may beprovided with a turbulent flow zone into which the individual brominefeed(s) or the feed mixture(s)/solution(s) containing bromine is/areinjected into the body of a turbulent reaction mixture as it is beingformed in the reaction zone.

A particularly preferred way of carrying out the above continuousprocess involves providing the bromination reaction zone with anupstream inlet zone and a downstream outlet zone; and conducting A) bycontinuously forming the reaction mixture by continuously feeding (i),(ii) and (iii), either separately or in combinations described above,into the upstream inlet zone. In this way, the reaction mixture iscontinuously produced in the reaction zone. Preferably such reactionmixture comprises a liquid phase in which bromination of styrenicpolymer can occur, the continuous travel of the reaction mixture in A)is from the upstream inlet zone to the downstream outlet zone, and atleast the average temperature of the liquid phase of the reactionmixture during such continuous travel is maintained at one or moretemperatures in the range of −20 to +20° C., preferably in the range of1 to 10° C., and more preferably in the range of 1 to 5° C. In addition,the exiting of the reaction mixture in A) from the reaction zonepreferably is from the downstream outlet zone, and the reaction mixtureas it exits from the reaction zone is passed into a quench zone in whichthe reaction mixture is quenched with a quenching composition comprisedof water in the liquid state.

In conducting a continuous process of this invention, it is generallydesirable to provide, maintain, and/or control the rate at which thereaction mixture exits from the reaction zone in A) in relation to therate of the feeding of components (i), (ii), and (iii) such that thevolume of the traveling contents of the reaction zone remainssubstantially constant. Thus, it is usually preferable to havecontinuous feeds to the reaction zone and continuous flows from thereaction zone, as this tends to make it easier to maintain anessentially constant volume in the reaction zone. However, it ispossible to use pulsed feeds to the reaction zone or one or more pulsedstreams exiting from the reaction zone while at the same time keepingthe volume of the reaction mixture in the reaction zone substantiallyconstant.

Termination of the bromination in B) of the continuous process istypically carried out by quenching reaction mixture that exits from thereaction zone with a quenching composition as or after such reactionmixture exits from the reaction zone. The quenching compositiontypically comprises water in the liquid state. The quenching step can becarried out either discontinuously or continuously. Discontinuousquenching involves collecting during a short period of time reactionmixture as it exits from the reaction zone and then promptly quenchingthat quantity in or with the quenching composition. Continuous quenchinginvolves causing the reaction mixture as it continuously exits from thereaction zone to be quenched in or with the quenching composition.

The makeup of the aqueous quenching composition can vary considerably.Typically however, the quenching composition will comprise at leastwater in the liquid state. An aqueous solution of one or more suitablesalts can also be used as a quenching composition. Non-limiting examplesof salts which may be used in forming quenching compositions includesodium sulfite, sodium bisulfite, and sodium borohydride. Temperaturesfor the quenching composition can also vary, but typically will be inthe range of 0 to 30° C. The concentration of the quenching compositioncomprised of one or more suitable salts in water is also susceptible tovariation. In actual practice, 1% to 10% solutions of sodium sulfite inwater have been found convenient for use as quenching compositions.However, other concentrations can be used. Use of water alone as thequenching composition is also possible.

Components Used as Feeds to the Reaction Zone

In both the batch/semi-batch mode of operation and the continuous modeof operation, various materials can be used as components (i), (ii), and(iii). For example, in all such modes of operation it is preferred touse elemental bromine as the brominating agent. The bromine should be ofhigh purity. Methods for purifying bromine when and if necessary ordesirable are described in many of the commonly-owned patents referredto at the outset of this document. However, other brominating agents canbe used in the practice of this invention. Among known brominatingagents that may be used are bromine chloride, N-bromosuccinimde,1,3-dibromohydantoin, and pyridinium tribromide.

Styrenic polymers which are brominated to form brominated styrenicpolymers using a process of this invention are homopolymers of styreneor copolymers of styrene with other vinyl aromatic monomers. Amongsuitable vinyl aromatic monomers from which the styrenic polymers can beformed are those having the formula:

H₂C═C(R)—Ar

wherein R is a hydrogen atom or an alkyl group having from 1 to 4 carbonatoms and Ar is an aromatic group (including alkyl-ring substitutedaromatic groups) of from 6 to 10 carbon atoms. Polystyrene itself is apreferred styrenic polymer, and anionic polystyrene is even morepreferred as the styrenic polymer to be brominated. Use can be madehowever of other styrenic polymers such as those made from at least 50weight percent, and more desirably at least 80 weight percent of styreneand/or alpha-methylstyrene with the balance being derived from ringsubstituted styrenic monomers. Thus, the “styrenic polymers” used in thepractice of this invention are polymers of one or more styrenic monomersin which at least 50%, preferably at least 80%, and more preferablyessentially 100% of the aromatic groups in the polymer have a hydrogenatom on at least one ortho position, and when the ring system of sucharomatic groups is composed of a combination of phenyl groups andalkyl-substituted phenyl groups, at least 50%, preferably at least 80%,and more preferably essentially 100% of all such phenyl groups have ahydrogen atom on each ortho position.

Examples of suitable monomers for producing such styrenic polymers arestyrene, alpha-methylstyrene, ortho-methylstyrene, meta-methylstyrene,para-methylstyrene, para-ethylstyrene, isopropenyltoluene,vinylnaphthalene, isopropenylnaphthalene, vinylbiphenyl,vinylanthracene, the dimethylstyrenes, and tert-butylstyrene.

The styrenic polymers used in the bromination processes of thisinvention are typically polymers made by cationic, by free radical, orby anionic polymerization procedures. An excellent process for producinganionic polystyrene is described in commonly-owned U.S. Pat. No.6,657,028. Styrenic polymers made by free radical initiation areavailable in the marketplace. Among such styrenic polymers that are wellsuited for use in forming brominated styrenic polymers pursuant to thisinvention is Styron®612 which is marketed by The Dow Chemical Company.However, additive-containing polystyrene such as Styron 668, Styron 677,Styron 680 of The Dow Chemical Company, as well as EA 3300, MB 3200, MC3100, or EA 3000 of Chevron Chemical Company, or equivalent materialsfrom other producers, can be used. Methods for producing cationicstyrenic polymers are known and reported in the literature. As betweenstyrenic polymers made by cationic polymerization and styrenic polymersmade by free radical polymerization, the latter styrenic polymers arepreferred. As between styrenic polymers made by free radicalpolymerization and styrenic polymers made by anionic polymerization, theanionic styrenic polymers are preferred.

Blends or mixtures of two or more styrenic polymers can also bebrominated using a bromination process of this invention. Such blends ormixtures can be composed of two or more different styrenic polymers madeby cationic polymerization, by free radical polymerization or by anionicpolymerization. A blend or mixture of at least one styrenic polymer madeby free radical polymerization and at least one styrenic polymer made byanionic polymerization can also be used as the polymer substrate to bebrominated by a process of this invention.

Anionic styrenic polymers used as raw materials in making brominatedstyrenic polymers of this invention will usually have GPC weight averagemolecular weights in the range of about 2000 to about 20,000 Daltons,preferably in the range of about 3000 to about 10,000 Daltons, and morepreferably in the range of about 3000 to about 7000 Daltons. Styrenicpolymers formed by free radical polymerization used as raw materials inbromination processes of this invention desirably have GPC weightaverage molecular weights in the range of about 30,000 to about 500,000Daltons, preferably in the range of about 50,000 to about 300,000Daltons, and more preferably in the range of about 150,000 to about300,000. Styrenic polymers formed by cationic polymerization used as rawmaterial in bromination processes of this invention desirably have GPCweight average molecular weights in the range of about 2000 to about20,000 Daltons, preferably in the range of about 3000 to about 10,000Daltons, and more preferably in the range of about 3000 to about 7000Daltons.

Any of a variety of suitable organic solvents can be used as the solventfor the styrenic polymer. Thus use can be made of such substances as,for example, dichloromethane, dibromomethane, bromochloromethane,bromotrichloromethane, chloroform, carbon tetrachloride,1,2-dibromoethane, 1,1-dibromoethane, 1-bromo-2-chloroethane,1,2-dichloroethane, 1,1,2-tribromoethane, 1,1,2,2-tetrabromoethane,1,2-dibromopropane, 1-bromo-3-chloropropane, 1-bromobutane,2-bromobutane, 2-bromo-2-methylpropane, 1-bromopentane,1,5-dibromopentane, 1-bromo-2-methylbutane, 1-bromohexane,1-bromoheptane, bromocyclohexane, and liquid isomers, homologs, oranalogs thereof. Liquid mixtures of two or more such compounds can beused. Bromochloromethane is a particularly preferred solvent.

Styrenic polymer is predis solved in the solvent prior to use in formingthe reaction mixture. The reaction zone in a batch or semi-batchoperation should contain a suitable quantity of organic solvent prior toinitiation of the feed of the components of the reaction mixture inorder to suspend or dissolve the catalyst. In a continuous mode ofoperation, a separate stream of additional solvent can be fed into thereaction zone, if desired.

With anionic styrenic polymers having a GPC weight average molecularweight in the range of about 3000 to about 10,000, preferably thestyrenic polymer solution used will contain in the range of 250 to 700grams of styrenic polymer per kilogram of solvent. With anionic styrenicpolymers of higher molecular weights the solutions should be more diluteto compensate for the increased viscosity of such polymer solutions.

As noted above, the catalyst as used in forming the reaction mixture isat least one aluminum halide catalyst in which the halogen atoms arebromine or chlorine atoms and in which at least one such atom is abromine atom. One such catalyst which is very useful in forming thereaction mixture is aluminum tribromide because of its good solubilityin bromine and halohydrocarbon solvents, such as dibromomethane andbromochloromethane. Aluminum halides containing both bromine atom(s) andchlorine atom(s) that may be used in forming the reaction mixtureinclude such substances as aluminum bromide dichloride (AlBrCl₂, Reg.No. 60284-44-8), aluminum dibromide chloride (AlBr₂Cl, Reg. No.60284-43-7), aluminum bromide chloride (Al₂Br₅Cl, Reg. No. 380907-74-4),and di-μ-bromotetrachlorodialuminum (Al₂Br₂Cl₄, Reg. No. 162719-12-2).In all of the embodiments of this invention, a preferred catalyst as fedto the reaction mixture is aluminum tribromide.

A catalyst solution suitable for either batch or continuous brominationcan be easily prepared by combining solid AlCl₃ (a substance which isnot soluble in bromine) and gaseous HBr in warm (40-50° C.) liquidbromine A rapid halogen exchange produces a soluble bromoaluminum halidecatalyst and HCl. Use of a catalyst of this type (with or without thecopresence of HCl) is particularly preferred.

Brominated Anionic Styrenic Polymers of the Invention

Novel brominated anionic styrenic polymers can be produced by use of theprocess technology of this invention. New brominated anionic styrenicpolymers of this invention have (i) higher melt flow indices as comparedto previously-known comparable brominated anionic styrenic polymers and(ii) high bromine contents. They also have low chlorine contents (e.g.,500 ppm or less, and preferably 100 ppm or less) and thus are lesscorrosive to equipment in which they are processed, such as blenders andextruders.

Preferred new brominated anionic styrenic polymers of this inventionhave high bromine contents and also have lower percentages of aromaticrings with ortho-substituted bromine atoms as compared topreviously-known comparable brominated anionic styrenic polymers.Typically the new brominated anionic styrenic polymers of thisinvention, especially those having a bromine content in the range ofabout 67 to about 71 wt %, have at least 5% less aromatic rings withortho-substituted bromine atoms as compared to previously-knowncomparable brominated anionic styrenic polymers. Indeed, experimentshave shown that brominated anionic polystyrenes of this invention havingbromine contents in the range of 67 to 69 wt % can have at least 10%less aromatic rings with ortho-substituted bromine atoms as compared topreviously-known comparable brominated anionic polystyrene.

More preferred new brominated anionic styrenic polymers of thisinvention also either have (A) a thermal stability in the 320° ThermalStability Test of 300 ppm or less of HBr (still more preferably 200 ppmof HBr or less and even more preferably 125 ppm of HBr or less) or (B)an initial ΔE color value of 5 or less (still more preferably 3 orless). Still more preferred new brominated anionic styrenic polymers ofthis invention also have both of these (A) and (B) properties. Novelbrominated anionic styrenic polymers of this invention are preferablybrominated anionic polystyrene polymers.

As used herein, including the claims, the term “previously-knowncomparable brominated anionic styrenic polymer(s)” denotes a brominatedstyrenic polymer that (1) is made from the same anionic styrenic polymerlot or made from an anionic styrenic polymer produced using the samekind of anionic polymerization initiator and the same kind of styrenicmonomer composition (i.e., both brominated styrenic polymers beingcompared are formed by bromination of anionic styrenic polymer that wasmade using the same kind and quantity of anionic polymerization system,and both such styrenic polymers prior to bromination were made bypolymerization of the same monomer such as styrene only, or if astyrenic copolymer, from the same styrenic monomers in the sameproportions); (2) has a bromine content above 66 wt % that differs fromthe bromine content of the new brominated anionic styrenic polymer ofthis invention (which also has a bromine content above 66 wt %) by nomore than 1.5 wt %; and (3) has a GPC weight average molecular weightthat differs from the average GPC weight average molecular weight of thetwo brominated anionic styrenic polymers being compared by no more than7.5%. In the foregoing, “previously-known” refers to informationpreviously made known to the public as part of the prior art.

Desirably, the GPC weight average molecular weight of the brominatedanionic styrenic polymers of this invention is in the range of about8000 to about 50,000 Daltons, preferably in the range of about 10,000 toabout 30,000 Daltons, and more preferably in the range of about 10,000to about 20,000 Daltons.

These novel brominated anionic styrenic polymers possess new and usefulproperties, especially improved melt flow properties and in many casessuperior initial color (typically measured as ΔE) and excellent thermalstability (typically measured by a standard thermal stability proceduredescribed hereinafter). On comparing NMR spectra, brominated anionicpolystyrene produced in accordance with this invention has more hydrogenatoms in the ortho ring positions than do products formed from the samecomponents in processes conducted under comparable reaction conditions,but involving longer feed times and use of cook periods. Also, a 2 to10° C. decrease in glass transition temperature observed for abrominated anionic polystyrene of this invention as compared tocomparable products produced with longer reaction residence times servesas additional evidence that the brominated anionic styrenic polymers ofthis invention are in fact different from previously known anionicstyrenic polymers. Thus the improved properties and analytical resultsboth point to novel chemical structure in the brominated styrenicpolymers of this invention, i.e., the bromine atoms in the brominatedstyrenic polymers of this invention tend to occupy positions other thanthe ortho position(s).

Whatever the mechanism, this invention provides as another embodimentbrominated anionic styrenic polymer produced by a process of thisinvention wherein the brominated anionic styrenic polymer when heated toa temperature and pressure at which a measurable flow of liquid polymeroccurs, has a higher melt flow than brominated anionic styrenic polymerproduced in a batch process in which (a) the same quantities andproportions of (i), (ii) and (iii) are fed for 30 minutes to a reactormaintained at the same reaction temperature and (b) the reaction mixturethen is held at the same temperature for a cook period of 5 minutes.

The new brominated anionic styrenic polymers of this invention arebrominated anionic styrenic polymers with brominated anionic polystyrenebeing particularly preferred. Of the brominated styrenic polymers madeusing free radical polymerization or cationic polymerization, brominatedpolystyrenes made using free radical polymerization are preferred.

Another desirable property of brominated styrenic polymers produced by abromination process of this invention—especially of the brominatedanionic styrenic polymers of this invention such as brominated anionicpolystyrene—is their high thermal stability in the 320° C. ThermalStability Test as described hereinafter. Preferred brominated styrenicpolymers, especially brominated anionic styrenic polymers such asbrominated anionic polystyrene, have a thermal stability in that test ofabout 300 ppm of HBr or less and more preferred such polymers have athermal stability in that test of about 200 ppm of HBr or less. Stillmore preferred brominated styrenic polymers of this invention,especially brominated anionic styrenic polymers such as brominatedanionic polystyrene, are those having a thermal stability in the 320° C.Thermal Stability Test of 125 ppm of HBr or less.

Still another feature of brominated styrenic polymers produced by aprocess of this invention—especially brominated anionic styrenicpolymers such as brominated anionic polystyrene—is their low colorvalues as illustrated by the Hunter Solution Color Value Test describedhereinafter. Preferred brominated styrenic polymers of this invention,especially brominated anionic styrenic polymers such as brominatedanionic polystyrene, are those which have an initial ΔE color value bythe Hunter test of 5 or less, and more preferably of 3 or less.

Especially preferred brominated styrenic polymers produced by a processof this invention—especially brominated anionic styrenic polymers suchas brominated anionic polystyrene—possess not only the improved meltflow characteristics described above, but in addition have either athermal stability in the 320° C. Thermal Stability Test or an initial ΔEColor Value as described in the immediately preceding two paragraphs.More especially preferred brominated styrenic polymers of this inventionpossess not only the improved melt flow characteristics described above,but in addition have both a thermal stability in the 320° C. ThermalStability Test and an initial ΔE Color Value as described in theimmediately preceding two paragraphs.

The brominated styrenic polymers that can be produced by the processesof this invention can contain any suitable amount of bromine. Typicallythey contain at least about 50 wt %, preferably at least about 60 wt %,and more preferably at least about 67 wt %. Bromine contents in therange of about 66 to about 71 wt %, and in the range of about 67 toabout 70 wt % are also desirable. Another desirable range is about 68 toabout 72 wt % of bromine.

Uses of Brominated Styrenic Polymers

The brominated styrenic polymers produced in accordance with thisinvention can be used as flame retardants for various polymericmaterials such as thermoplastic and thermosetting polymeric materialsand resins. The improved melt flow characteristics of the brominatedanionic styrenic polymers of this invention enhances their usefulnessfor such applications. For example, their improved melt flow enablesthem to be melt blended more readily with thermoplastic polymers, and tobe more readily applied to thermoset polymers or resins as coatings oras flame retardant binders. The weight average molecular weights of thesubstrate polymers that can be flame retarded pursuant to this inventioncan vary widely, from low molecular weight polymers to very highmolecular weight polymers. Methods for producing the variousthermoplastic or thermosetting polymers that can be flame retarded withthe brominated styrenic polymers of this invention are known to those ofordinary skill in the art. Other persons who may be unfamiliar with suchmatters, should refer to the extensive literature that exists on suchsubjects.

Preferably the brominated styrenic polymers of this invention are usedas additive flame retardants for various thermoplastic polymers. Thusamong the embodiments of this invention are flame retardant compositionscomprising at least one thermoplastic polymer and a flame retardantquantity of at least one brominated anionic styrenic polymer of thisinvention.

Particular thermoplastics with which the brominated anionic styrenicpolymers of this invention can be blended pursuant to furtherembodiments of this invention include polyethylene terephthalate,polybutylene terephthalate, polycyclohexylene dimethylene terephthalate,polytrimethylene terephthalate, blends or mixtures of two or more ofthese, and analogous copolymeric thermoplastic polyesters, especiallywhen filled or reinforced with a reinforcing filler such as glass fiber.Preferred thermoplastic polyesters are polyethylene terephthalate andpolybutylene terephthalate. Polyamide thermoplastics, such as polyamide6, polyamide 6,6, polyamide 12, etc., again preferably when glassfilled, can also be effectively flame retarded in like manner. Otherthermoplastic polymers that can be effectively flame retarded byaddition of a brominated styrenic polymer of this invention include butare not limited to styrenic polymers, high impact polystyrenes, crystalpolystyrenes, polyolefins, ABS, MABS, SAN, aromatic polycarbonates,polyphenylene ethers, and polymer blends such as aromaticpolycarbonate-ABS blends, polyphenylene ether-polystyrene blends, andsimilar substances. One group of thermoplastic polymers which can beeffectively flame retarded by use of at least one brominated anionicstyrenic polymer of this invention is (1) a thermoplastic styrenicpolymer, (2) a thermoplastic acrylonitrile-butadiene-styrene polymer,(3) a thermoplastic polyester, or (4) a thermoplastic polyamide.Conventional additives, such as flame retardant synergists,antioxidants, UV stabilizers, pigments, impact modifiers, fillers, acidscavengers, blowing agents, and the like, can be included with theformulations as is appropriate. Preferred polymer blends of thisinvention do contain a flame retardant synergist or glass fiber filleror reinforcement, and most preferably both a synergist, and areinforcing fiber and/or filler.

The brominated styrenic polymer formed by a process of this invention Band especially brominated anionic styrenic polymers such as brominatedanionic polystyrene of this invention B are used in flame retardantamounts, which typically are within the range of from about 5 to about25 wt %, the wt % being based on the total weight of the thermoplasticpolymer formulation or blend. When used, the amount of reinforcingfillers such as glass fiber will typically be in the range of up toabout 50 wt % based on the total weight of the finished composition. Theamount of flame retardant synergist, when used, such as antimonytrioxide, antimony pentoxide, sodium antimonate, potassium antimonate,iron oxide, zinc borate, or analogous synergist generally will be in therange of up to about 12 wt % based on the total weight of the finishedcomposition. Departures from the foregoing ranges of proportions arepermissible whenever deemed necessary or desirable under the particularcircumstances at hand, and such departures are within the scope andcontemplation of this invention.

Masterbatch compositions wherein the components except for the substratethermoplastic polymer are in suitable relative proportions but areblended in a smaller amount of the substrate polymer, are also withinthe scope of this invention. Thus this invention includes compositionswhich comprise at least one thermoplastic polymer such as a polyalkyleneterephthalate or a nylon polymer or a high impact polystyrene with whichhas been blended a brominated anionic styrenic polymer (preferably abrominated anionic polystyrene) of this invention in a weight ratio(substrate polymer:brominated anionic styrenic polymer or polystyrene)in the range of, say, 1:99 to 70:30. Such masterbatch blends need not,but may also contain filler or reinforcing fiber and/or at least oneflame retardant synergist such as iron oxide, zinc borate, or preferablyan antimony oxide synergist such as antimony trioxide, antimonypentoxide, sodium antimonate, or potassium antimonate. Typical examplesof reinforcing agents or fillers that can be used include low-alkaliE-glass, carbon fibers, potassium titanate fibers, glass spheres ormicroballoons, whiskers, talc, wollastonite, kaolin, chalk, calcinedkaolin, and similar substances. Sizing agents can be used with suchreinforcing agents or fillers, if desired. A number of suitableglass-filled polyalkylene terephthalates or nylon molding compositionsare available on the open market, and these can be used in preparing thecompositions of this invention.

Also provided by this invention are additive blends composed of abrominated anionic styrenic polymer of this invention and a synergistsuch as, for example, a blend of 75 parts by weight of a brominatedanionic polystyrene and 25 parts by weight of a synergist such asantimony trioxide, antimony pentoxide, sodium antimonate, potassiumantimonate, iron oxide, zinc borate, or analogous synergist. Typicallysuch blends will contain in the range of about 70 to about 98 parts byweight of the brominated anionic polystyrene and about 30 to about 2parts by weight of the synergist, with the total of the two componentsbeing 100 parts by weight. Suitable amounts of other suitable additivecomponents can also be included in such additive blends.

Various known procedures can be used to prepare the blends orformulations constituting such additional compositions of thisinvention. For example the polyalkylene terephthalate polymer or a nylonpolymer and the brominated styrenic polymer such as brominatedpolystyrene and any other components or ingredients to be incorporatedinto the finished blend can be blended together in powder form andthereafter molded by extrusion, compression, or injection moldingLikewise the components can be mixed together in a Banbury mixer, aBrabender mixer, a roll mill, a kneader, or other similar mixing device,and then formed into the desired form or configuration such as byextrusion followed by comminution into granules or pellets, or by otherknown methods.

Preferred thermoplastic compositions of this invention have thecapability of forming molded specimens of 1.6 and 3.2 millimeterthickness ( 1/16 and ⅛-inch thickness) that pass at least the UL 94 V2test.

Analytical Methods

Known analytical methods can be used or adapted for use in assaying thecharacteristics of the polymers of this invention. However, thefollowing methods should be used for the sake of consistency.

Total Bromine Content. Since brominated styrenic polymers have good, orat least satisfactory, solubility in solvents such as tetrahydrofuran(THF), the determination of the total bromine content for the brominatedstyrenic polymers is easily accomplished by using conventional X-RayFluorescence techniques. The sample analyzed is a dilute sample, say0.1±0.05 g brominated polystyrene in 60 mL THF. The XRF spectrometer canbe a Phillips PW 1480 Spectrometer. A standardized solution ofbromobenzene in THF is used as the calibration standard. The totalbromine values described herein and reported in the Examples are allbased on the XRF analytical method.

Hunter Solution Color Value Test. To determine the color attributes ofthe brominated polymers of this invention, use is again made of theability to dissolve brominated styrenic polymers in easy-to-obtainsolvents, such as chlorobenzene. The analytical method used is quitestraight-forward. Weigh 5 g±0.1 g of the brominated polystyrene into a50 mL centrifuge tube. To the tube also add 45 g±0.1 g chlorobenzene.Close the tube and shake for 1 hour on a wrist action shaker. After the1 hour shaking period, examine the solution for undissolved solids. If ahaze is present, centrifuge the solution for 10 minutes at 4000 rpm. Ifthe solution is still not clear, centrifuge an additional 10 minutes.Should the solution remain hazy, then it should be discarded as beingincapable of accurate measurement. If, however, and this is the casemost of the time, a clear solution is obtained, it is submitted fortesting in a HunterLab Color Quest Sphere Spectrocolorimeter. Atransmission cell having a 20-mm transmission length is used. Thecolorimeter is set to “Delta E-lab” to report color as ΔE and to givecolor values for “L”, “a” and “b”. Product color is determined as totalcolor difference (ΔE) using Hunter L, a, and b scales for the 10% byweight concentrations of the product in chlorobenzene versuschlorobenzene according to the formula:

ΔE=[(ΔL)²⁺(Δa)²⁺(Δb)²]^(1/2)

DSC Values. DSC values were obtained with a TA Instruments DSC Model2920. Samples were heated from 25° C. to 400° C. at 10° C./min undernitrogen.

Thermogravimetric Analysis. Thermogravimetric analysis (TGA) is alsoused to test the thermal behavior of the brominated styrenic polymers ofthis invention. The TGA values are obtained by use of a TA InstrumentsThermogravimetric Analyzer. Each sample is heated on a Pt pan from 25°C. to about 600° C. at 10° C./min with a nitrogen flow of 50-60 mL/min.

320° C. Thermal Stability Test. To determine thermal stability andestimate the corrosive potential of a sample, the 320° C. ThermalStability Test is used. The test procedure essentially as described inU.S. Pat. No. 5,637,650 except that the temperature used is 320° C.instead of 300° C. The reason for using such higher temperature is thatthe polymers of this invention do not involve measurable amounts of HBrat 300° C. Thus, in conducting this test, each sample is run induplicate. A 2.00±0.01 g sample is placed into a new clean 20×150 mmtest tube. With a neoprene stopper and Viton® fluoroelastomer tubing,the test tube is connected to a nitrogen purge line with exit gas fromthe test tube being passed successively through subsurface gasdispersion frits in three 250-mL sidearm filter flasks each containing200 mL of 0.1 N NaOH and 5 drops of phenolphthalein. With a constantnitrogen purge at 0.5 SCFH, the test tube is heated at 320° C. in amolten salt bath (51.3% KNO₃/48.7% NaNO₃) for 15 minutes followed by 5minutes at ambient temperature. The test tube containing the sample isthen replaced with a clean dry test tube, and the apparatus is purgedwith nitrogen for an additional 10 minutes with the empty test tube inthe 320° C. salt bath. The test tube, tubing and gas dispersion tubesare all rinsed with deionized water, and the rinse is combinedquantitatively with the solutions in the three collection flasks. Thecombined solution is acidified with 1:1 HNO₃ and titrated with 0.01 NAgNO₃ using an automatic potentiometric titrator (Metrohm 670, 716, 736,or equivalent). Results are calculated as ppm HBr, ppm HCl, and ppm HBrequivalents as follows:

ppm HBr=(EP 1)(N)(80912)/(sample wt.)

ppm HCl=(EP 2−EP 1)(N)(36461)/(sample wt.)

ppm HBr equivalents=(EP 2)(N)(80912)/(sample wt.)

where EP(x)=mL of AgNO₃ used to reach end point x; and N=normality ofAgNO₃. The tubing is thoroughly dried with nitrogen before the nextanalysis. Each day before the first sample, three empty clean test tubesare run as blanks to assure there is no residual hydrogen halide in thesystem.

NMR Analyses

Proton NMR spectra are acquired using a Bruker DPX 400 MHz instrument ata probe temperature of 120° C. for solutions of about 20 wt % brominatedpolystyrene in 1,1,2,2,-tetrachloroethane-d₂. After normal processingand base line corrections, the area of the broad peaks are integratedbetween 3.8 to 2.2 ppm and 2.2 to 0.9 ppm. The sum of these two areas,after correction for end groups and residual solvent, represents thethree chain protons per polymer repeat unit. The area from 3.8 to 2.2ppm represents the chain methine proton where the associated aromaticring has at least one ortho-bromine atom. The percentage of polymerunits having ortho ring bromination is determined from these integrals.

GPC Weight Average Molecular Weights

The M_(w) values were obtained by GPC using a Waters model 510 HPLC pumpand, as detectors, a Waters Refractive Index Detector, Model 410 and aPrecision Detector Light Scattering Detector, Model PD2000. The columnswere Waters, μStyragel, 500 Å, 10,000 Å and 100,000 Å. The autosamplerwas a Shimadzu, Model Sil 9 Å. A polystyrene standard (M_(w)=185,000)was routinely used to verify the accuracy of the light scattering data.The solvent used was tetrahydrofuran, HPLC grade. The test procedureused entailed dissolving 0.015-0.020 g of sample in 10 mL of THF. Analiquot of this solution is filtered and 50 μL is injected on thecolumns. The separation was analyzed using software provided byPrecision Detectors for the PD 2000 Light Scattering Detector.

Melt Flow Index Test. To determine the melt flow index of the brominatedstyrenic polymers of this invention, the procedure and test equipment ofASTM Test Method D1238-00 are used. The extrusion plastometer isoperated at 2.16 kg applied pressure and at a temperature selected from220° C., 235° C., or 270° C. that provides measurable flow of the moltenpolymer sample being analyzed. The samples used in the tests are abrominated styrenic polymer of this invention or a sample of one or morepreviously-known comparable brominated styrenic polymers with which thepolymer of this invention is being compared. All such tests are runusing neat unadulterated samples of each of the respective polymers.

As used throughout this application, “APS” is used interchangeably withand meant to designate anionic polystyrene. The term “BrAPS” designatesbrominated anionic polystyrene. The term “M_(w)” means weight averagemolecular weight and the term “M_(n)” means number average molecularweight, both as determined by GPC (light scattering detector) describedabove. The term “CSTR” means continuous stirred tank reactor.

The following numbered Examples illustrate the practice of thisinvention and are not intended to limit the generic scope of thisinvention. Also presented for reference purposes are lettered Examplesillustrating the preparation and properties of brominated styrenicpolymers formed using the best previously-known process technology. Itwill be noted that the Reference Examples utilized relatively longreaction or residence times whereas pursuant to this invention theExamples of the invention involve use of relatively short reaction orresidence times. Comparison of the results of these respective Examplesthus illustrate some of the advantages provided by this invention.

Reference Example A

This batch bromination was carried out using an anionic polystyrenehaving a number average molecular weight of 2900 and a weight averagemolecular weight of 3400. A 2.46 g (18.5 mmol) portion of aluminumchloride (Aldrich) was suspended in 645.9 g of dry (>15 ppm water) BCMin a 1-L, 5-necked, jacketed, glass reaction flask cooled to −6° C. by acirculating glycol bath. The reaction flask having a flush-mount Teflonpolymer bottom valve was equipped with an overhead air stirrer andTeflon polymer banana-blade paddle, Friedrich's condenser (glycolcooled), and thermowell. A constant flow of dry nitrogen was maintainedon the vent line from the condenser to assist in moving exit gases fromthe flask to a caustic scrubber. A 335.37 g portion of a 40.0 wt %solution (134.2 g APS, 1.29/n mol) of the anionic polystyrene in dry BCMwas charged to a 500-mL graduated cylinder in a dry box. The graduatedcylinder was then set up to pump the APS solution from the cylinder to ajacketed, glycol-cooled glass mixing tee mounted on the reaction flask.Bromine (555.7 g, 3.48 moles, 2.70 equivalents) was charged to a 250-mLgraduated cylinder and set up to pump the bromine to the same mixing teeas the APS solution. Both streams were cooled separately by the mixerbefore combining at the bottom of the apparatus and dropping into thebromination flask. The reaction mixture was protected fromphoto-initiated aliphatic bromination by turning off hood lights andwrapping the flask and mixing tee with Al foil. Both feeds were startedat the same time and were both completed in 80 min. A rinse of 102 g ofdry BCM was used for the APS solution feed system to assure completetransfer of the polymer to the reaction flask while nitrogen was flushedthrough the bromine feed system to give quantitative transfer of thebromine. The reaction temperature was maintained at −2° C. to −4° C.throughout the addition and subsequent 15 min cook period (with nitrogenpurge of the reactor overhead). The catalyst was deactivated by additionof 50 g of water. A 200 g portion of 10 wt % aqueous sodium sulfite wasthen added to assure the removal of any residual bromine. The organicphase was separated, and then washed with water (4×1 L) until neutral.The product was recovered from the organic phase by addition tovigorously stirred hot (98° C.) water. The solvent distilled from thehot water leaving a slurry of the brominated polystyrene product inwater. After suction filtering, the white solid was rinsed with water(3×2L) and dried to a constant weight of 399.2 g (97% yield) in an oven(123° C.) under a constant nitrogen purge. Product analyses appear inTable 1.

Example 1

This continuous bromination was carried out using an anionic polystyrenehaving a number average molecular weight of 3200 and a weight averagemolecular weight of 3300 with three feed streams to the reactor. An80-mL capacity glass CSTR was used for the run. The reactor had an outerinsulating vacuum jacket and an inner jacket for circulating glycolcoolant. The vessel had three inlet ports on the bottom for delivery ofreagent solutions directly under the bottom turbine blade of the dualTeflon polymer turbine agitator (operated at 400 rpm). An overflow portlocated just above the top turbine blade allowed the reaction mixture toflow by gravity to a splitter that could direct the flow to the mainproduct quench pot (5-L fully jacketed round bottom flask with paddlestirrer) or a secondary waste quench pot (2-L Erlenmeyer with magneticstirrer). Exit gases from the CSTR passed overhead through a Friedrich'scondenser and into an aqueous caustic scrubber with assistance from aconstant nitrogen purge at the top of the condenser. During thebromination, the room and hood lights were turned off to minimizephotobromination.

A single pump motor (Ismatec peristaltic pump, Cole-Parmer SY-78017-00)having two pump heads was used to deliver equal volumes of bromine andPS solutions to the CSTR using feed lines of Teflon polymer (⅛″) andViton fluoroelastomer (0.10″, Cole-Parmer, SY-07605-46). A separateperistaltic pump (Masterfiex 7550-90) was used to feed the AlBr₃/CH₂Br₂solution using a feed line of Teflon polymer (⅛″) and Vitonfluoroelastomer (#14).

The concentrations of the BCM solutions of APS (30.0 wt %, d=1.545 g/mL)and bromine (72.1 wt %, d=2.660 g/mL) were chosen so that equal volumeswould provide 2.7 equivalents of bromine for each aromatic ring in theAPS. By using a single pump to transfer equal volumes of these twosolutions to the reactor, pulsations of the two feed streams are matchedand essentially no instantaneous change in stoichiometry is expected tooccur during the operation of the CSTR. The standard insoluble AlCl₃bromination catalyst used in the batch process was replaced by thesoluble AlBr₃. A commercially available (Aldrich) 1.0 molar 10.58 wt %AlBr₃ solution of AlBr₃ in dibromomethane (DBM) was used. BCM can not beused in place of DBM for AlBr₃ dissolution due to halogen exchange thatconverts the soluble bromide to the insoluble chloride in a matter ofseveral minutes at room temperature.

The operation was started by charging the CSTR with dry BCM (150.5 g)and 8 mL of the AlBr₃ solution. After cooling the contents of the CSTRto −9° C., the bromine and APS feeds were started (4.8 mL/min rate foreach stream), and the AlBr₃ feed rate was adjusted to a pump setting of0.35 ml/min. The CSTR temperature quickly rose to +1° C. and then slowlyincreased to reach +3° C. by the end of the operation. For the first 26min, the overflow stream from the CSTR was directed to the waste quenchpot (containing 850 g of 2 wt % aqueous Na₂SO₃). At this point, it wasassumed a steady state condition (over 3 residence times) had beenreached, so the overflow stream was diverted to the main quench pot(containing 1590 g of 2 wt % aqueous Na₂SO₃) to collect the steady stateproduct until the PS solution was completely used (48 min). A smallamount (41.0 g) of bromine solution remained unused. The weights of feedsolutions used for the 74 min of operation were:

1) 30.0 wt % APS in BCM, 619.26 g (1.78 mol)

2) 72.1 wt % Br₂ in BCM, 1026.0 g, (4.63 mol), 2.60 equiv.

3) 10.6 wt % AlBr₃ in DBM, 84.9 g (0.0337 mol), 1.89 mol %

The white organic phase (934.7 g) in the main quench pot was separatedfrom the aqueous phase, and combined in a 2-L separatory funnel with aBCM rinse (143.7 g) of the quench vessel. Three aqueous washes (900 geach) were used to remove residual acid and salts. The neutralized whiteorganic phase was pumped into 5-L of vigorously stirred hot (98° C.)water to obtain a slurry of white finely divided solid in water. Theslurry was suction filtered, and the solid was rinsed on the filter withwater (3×2L). The wet cake (588 g) was dried in a nitrogen purged ovenat 122° C. to a constant weight of 389.8 g. Analytical results aresummarized in Table 1.

Reference Example B

This batch bromination was carried out using an anionic polystyrenehaving a number average molecular weight of 2900 and a weight averagemolecular weight of 5700. A 2.75 g (20.6 mmol) portion of aluminumchloride (Aldrich) was suspended in 550.3 g of dry (>15 ppm water) BCMin a 1-L, 5-necked, jacketed, glass reaction flask cooled to −8° C. by acirculating glycol bath. The reaction flask having a flush-mount Teflonpolymer bottom valve was equipped with an overhead air stirrer andTeflon polymer banana-blade paddle, Friedrich's condenser (glycolcooled), and thermowell. A constant flow of dry nitrogen was maintainedon the vent line from the condenser to assist in moving exit gases fromthe flask to a caustic HBr scrubber. A 374.92 g portion of a 40.0 wt %solution (149.97 g APS, 1.44/n mol) of the anionic polystyrene in dryBCM was charged to a 500-mL graduated cylinder in a dry box. Thegraduated cylinder was then set up to pump the APS solution from thecylinder to a jacketed, glycol-cooled glass mixing tee mounted on thereaction flask. Bromine (621.6 g, 3.890 moles, 2.70 equivalents) wascharged to a 250-mL graduated cylinder and set up to pump the bromine tothe same mixing tee as the APS solution. Both streams were cooledseparately by the mixer before combining at the bottom of the apparatusand dropping into the bromination flask. The reaction mixture wasprotected from photo-initiated aliphatic bromination by turning off hoodlights and wrapping the flask and mixing tee with Al foil. Both feedswere started at the same time and were both completed in 72 min. A rinseof 112 g of dry BCM was used for the APS solution feed system to assurecomplete transfer of the polymer to the reaction flask while nitrogenwas flushed through the bromine feed system to give quantitativetransfer of the bromine. The reaction temperature was maintained at −3°C. to −5° C. throughout the addition and subsequent 15 min cook period(with nitrogen purge of the reactor overhead). The catalyst wasdeactivated by addition of 50 g of water. A 86.4 g portion of 10 wt %aqueous sodium sulfite was then added to assure the removal of anyresidual bromine. The organic phase was separated, and then washed withwater (4×1 L) until neutral. The product was recovered from the organicphase by addition to vigorously stirred hot (98° C.) water. The solventdistilled from the hot water leaving a slurry of the brominatedpolystyrene product in water. After suction filtering, the white solidwas rinsed with water (3×2L) and dried to a constant weight of 443.8 g(96% yield) in an oven (118° C.) under a constant nitrogen purge.Product analyses appear in Table 1.

Example 2

This continuous bromination was carried out as described in Example 1using an anionic polystyrene having a number average molecular weight of2900 and a weight average molecular weight of 5700. The operation wasstarted by charging the CSTR with dry BCM (149.8 g) and 9 mL of theAlBr₃ solution. After cooling the contents of the CSTR to −12° C., thebromine and APS feeds were started (4.8 mL/min rate for each stream),and the AlBr₃ feed rate was adjusted to a pump setting of 0.21 ml/min.The CSTR temperature stayed between +1° C. and +3° C. during thereaction. For the first 25 min, the overflow stream from the CSTR wasdirected to the waste quench pot (containing 1034 g of 2 wt % aqueousNa₂SO₃). At this point, it was assumed a steady state condition (over 3residence times) had been reached, so the overflow stream was divertedto the main quench pot (containing 1757 g of 2 wt % aqueous Na₂SO₃) tocollect the steady state product until the APS solution was depleted (70min). A small amount (66.6 g) of bromine solution remained unused. Theweights of feed solutions used for the 95 min of operation were:

1) 30.0 wt % APS in BCM, 801.1 g (2.30 mol)

2) 72.3 wt % Br₂ in BCM, 1319.8 g, (5.97 mol), 2.60 equiv.

3) 10.6 wt % AlBr₃ in DBM, 82.6 g (0.0327 mol), 1.42 mol %

The white organic phase (1224.0 g) in the main quench pot was separatedfrom the aqueous phase, and combined in a 2-L separatory funnel with aBCM rinse (205 g) of the quench vessel. Four aqueous washes were used toremove residual acid and salts. The neutralized white organic phase waspumped into 5-L of vigorously stirred hot (98° C.) water to obtain aslurry of white finely divided solid in water. The slurry was suctionfiltered, and the solid was rinsed on the filter with water (3×2L). Thewet cake (850 g) was dried in a nitrogen purged oven at 130° C. to aconstant weight of 521.3 g. Analytical results are summarized in Table1.

Reference Example C

This batch bromination was carried out as described in Reference ExampleB using an anionic polystyrene having a number average molecular weightof 3600 and a weight average molecular weight of 7500. Analyticalresults for the product are summarized in Table 1.

Example 3

This continuous bromination was carried out as described in Example 1using an anionic polystyrene having a number average molecular weight of3600 and a weight average molecular weight of 7500. Product analyses aresummarized in Table 1.

TABLE 1 BATCH AND CONTINUOUS BROMINATION REACTIONS Example Ref A 1 Ref B2 Ref C 3 Bromination Process Batch Continuous Batch Continuous BatchContinuous Catalyst AlCl₃ AlBr₃ AlCl₃ AlBr₃ AlCl₃ AlBr₃ AlX₃, mole %1.43 1.89 1.43 1.42 1.45 1.45 Maximum reaction Temp (°C.) −1 +4 −3 +3 −4+2 Total reaction time or 80 8 87 8 88 8 avg. residence time (min) APSfeed 40.0 30.0 40.0 30.0 38.9 30.0 concentration (wt %) APS M_(n) 29003200 2900 2900 3600 3600 APS M_(w) 3400 3300 5700 5700 7500 7500 BrAPSProduct Analyses Wt % Br (XRF) 68.9 67.4 68.8 68.4 69.1 69.0 ThermalHBr, 320° C./15 min/N₂ (ppm) 187 59 115 112 77 99 Thermal color, (320°C./15 min/N2), 10 wt % in chlorobenzene L 93.46 95.29 95.41 95.34 95.0494.36 a −2.31 −2.69 −3.59 −2.55 −5.12 −2.85 b 19.11 17.17 16.04 15.2122.91 16.81 ΔE 20.39 18.02 17.06 16.14 23.86 18.01 Initial Color, 10 wt% in chlorobenzene L 99.34 99.84 99.92 99.50 99.72 99.73 a −0.53 0.38−0.51 0.24 −0.21 −0.04 b 2.59 −0.13 2.27 1.07 1.63 1.83 ΔE 2.84 0.182.35 1.32 1.77 1.93 DSC, T_(g) (° C.) 159.9 158.2 160.6 155.6 169.2161.8 TGA 1% wt loss temp, N₂ (° C.) 351.1 343.7 349.6 350.7 359.0 350.8BrAPS GPC M_(n) 12,100 12,400 13,200 13,000 18,200 15,300 M_(w) 13,10013,000 22,400 22,100 29,600 28,700 % Aromatic rings with ortho-Br (NMR)77.8 67.4 82.4 68.0 81.6 70.8 MFI (g/10 min, 220° C./2.61 kg) 9.5 19.03.3 12.1 1.0 2.4

The brominated anionic polystyrenes of Examples 1 and 2 are novelproducts of this invention having extremely low initial solution ΔEvalues. These brominated anionic polystyrenes also possess other highlydesirable properties such as high bromine contents, high thermalstabilities in the 320° C. Thermal Stability Test, and GPC weightaverage and GPC number average weights in ranges which enable them to bereadily blended with a wide variety of thermoplastic polymers. So far asis presently known, the lowest value initial solution ΔE value reportedfor a brominated anionic polystyrene is 1.74, and that polymer had a farinferior thermal stability in the Thermal Stability Test even thoughconducted at 300° C. rather than at 320° C. as in Examples 1 and 2above, and a significantly higher GPC weight average molecular weight.See in this connection, U.S. Pat. No. 6,521,714, e.g., Column 33, lines55-67, Column 34, lines 32-67, and Table VI, Example CE-6.

Reference Example D

This batch bromination was carried out as described in Reference ExampleA using an anionic polystyrene having a number average molecular weightof 3400 and a weight average molecular weight of 3800. A 1.22 g (9.15mmol) portion of aluminum chloride was suspended in 499.1 g of dry (>15ppm water) BCM in a 1-L, 5-necked, jacketed, glass reaction flask cooledto −5° C. by a circulating glycol bath. The reaction flask, having aflush-mount Teflon polymer bottom valve, was equipped with an overheadair stirrer and Teflon polymer banana-blade paddle, Friedrich'scondenser (glycol cooled), and thermowell. A constant flow of drynitrogen was maintained on the vent line from the condenser to assist inmoving exit gases from the flask to a caustic scrubber forneutralization of the HBr by-product. A 315.0 g portion of a 40.5 wt %solution (127.6 g APS, 1.23/n mol) of anionic polystyrene in dry BCM wascharged to a 250-mL graduated cylinder in a dry box. The graduatedcylinder was then set up to pump the APS solution from the cylinder to ajacketed, glycol-cooled glass mixing tee mounted on the reaction flask.Bromine (529.3 g, 3.31 moles, 2.70 equivalents) was charged to a 250-mLgraduated cylinder and set up to pump the bromine to the same mixing teeas the APS solution. Both streams were cooled separately by the mixerbefore combining at the bottom of the apparatus and dropping into thebromination flask. The reaction mixture was protected fromphoto-initiated aliphatic bromination by turning off hood lights andwrapping the flask and mixing tee with Al foil. Both feeds were startedat the same time and were both completed in 60 min. The reactiontemperature was maintained at −2° C. to 0° C. throughout the additionand subsequent 15 min cook period (with nitrogen purge of the reactoroverhead). The catalyst was deactivated by addition of 40 g of water. A19.2 g portion of 10 wt % aqueous sodium sulfite was then added toassure the removal of any residual bromine. The organic phase wasseparated, and then washed with water, dilute sodium hydroxide, andfinally water to neutralize acid and remove NaBr. The product wasrecovered from the organic phase by addition to 4-L of vigorouslystirred hot (98° C.) water. The solvent distilled from the hot waterleaving a slurry of the brominated polystyrene product in water. Aftersuction filtration of the slurry, the white solid was rinsed with water(3×2L) and dried to a constant weight of 378.9 g (97% yield) in an oven(130° C.) under a constant nitrogen purge. Product analyses are given inTable 2.

Reference Example E

This batch bromination was carried out as described in Reference ExampleD using the same anionic polystyrene, but with a higher AlCl₃ level.Both the bromine and APS feeds were started at the same time and wereboth completed in 61 min. The reaction temperature was maintained at −2°C. to +1° C. throughout the addition and subsequent 15 min cook period(with nitrogen purge of the reactor overhead). The catalyst wasdeactivated by addition of 40 g of water. A 26.5 g portion of 10 wt %aqueous sodium sulfite was then added to assure the removal of anyresidual bromine. The organic phase was separated, and then washed withwater, dilute sodium hydroxide, and finally water to neutralize acid andremove NaBr. The product was recovered from the organic phase byaddition to vigorously stirred hot (98° C.) water. The solvent distilledfrom the hot water leaving a slurry of the brominated polystyreneproduct in water. After suction filtering, the white solid was rinsedwith water (3×2L) and dried to a constant weight of 382.5 g (98% yield)in an oven (130° C.) under a constant nitrogen purge. Product analysesare given in Table 2.

Reference Example F

This batch bromination was similar to Reference Example E using the sameanionic polystyrene, but AlCl₃ was replaced with AlBr₃ catalyst and thereaction time was reduced from a total time of 75 min to 35 min. A 2.53g (9.49 mmol) portion of aluminum bromide (Alfa) was suspended in 772.4g of dry (>15 ppm water) BCM in a 1-L, 5-necked, jacketed, glassreaction flask cooled to −3° C. by a circulating glycol bath. Thereaction flask, having a flush-mount Teflon polymer bottom valve, wasequipped with an overhead air stirrer and Teflon polymer banana-bladepaddle, Friedrich's condenser (glycol cooled), and thermowell. Aconstant flow of dry nitrogen was maintained on the vent line from thecondenser to assist in moving exit gases from the flask to a causticscrubber. A 174.3 g portion of a 40.5 wt % solution (70.6 g APS, 0.678/nmol) of anionic polystyrene in dry BCM was charged to a 250-mL graduatedcylinder in a dry box. The graduated cylinder was then set up to pumpthe APS solution from the cylinder to a jacketed, glycol-cooled glassmixing tee mounted on the reaction flask. Bromine (289.9 g, 1.814 moles,2.68 equivalents) was charged to a 200-mL graduated cylinder and set upto pump the bromine to the same mixing tee as the APS solution. Bothstreams were cooled separately by the mixer before combining at thebottom of the apparatus and dropping into the bromination flask. Thereaction mixture was protected from photo-initiated aliphaticbromination by turning off hood lights and wrapping the flask and mixingtee with Al foil. Both feeds were started at the same time and were bothcompleted in 30 min A rinse of 100 g of dry BCM was used for the APSsolution feed system to assure complete transfer of the polymer to thereaction flask while nitrogen was flushed through the bromine feedsystem to give quantitative transfer of the bromine. The reactiontemperature was maintained at +1° C. to +3° C. throughout the additionand subsequent 5 min cook period (with nitrogen purge of the reactoroverhead). The catalyst was deactivated by addition of 40 g of water. A12.8 g portion of 10 wt % aqueous sodium sulfite was then added toassure the removal of any residual bromine. The organic phase wasseparated, and then washed with water, dilute sodium hydroxide, andfinally water to neutralize acid and remove NaBr. The product wasrecovered from the organic phase by addition to vigorously stirred hot(98° C.) water. The solvent distilled from the hot water leaving aslurry of the brominated polystyrene product in water. After suctionfiltering the slurry, the white solid was rinsed with water (3×2L) anddried to a constant weight of 205.4 g (96% yield) in an oven (130° C.)under a constant nitrogen purge. Product analyses are given in Table 2.

Example 4

This continuous bromination used the same anionic polystyrene used inReference Examples D, E, and F (number average molecular weight of 3400and a weight average molecular weight of 3800) with only two feedstreams to the reactor. The bromine stream, containing the dissolvedAlBr₃ catalyst, and the APS solution in BCM were metered to the reactorusing two separate pumps. An 80-mL capacity glass CSTR was used for thereaction. The reactor had an outer insulating vacuum jacket and an innerjacket for circulating glycol coolant. The vessel had two inlet ports onthe bottom for delivery of reagent solutions directly under the bottomturbine blade of the dual Teflon polymer turbine agitator (operated at400 rpm). An overflow port located just above the top turbine bladeallowed the reaction mixture to flow by gravity to a splitter that coulddirect the flow to the main product quench pot (5-L fully jacketed roundbottom flask with paddle stirrer) or a secondary waste quench pot (2-LErlenmeyer with magnetic stirrer). Exit gases from the CSTR passedoverhead through a Friedrich's condenser and into an aqueous causticscrubber with assistance from a constant nitrogen purge at the top ofthe condenser. During the bromination, the room and hood lights wereturned off to minimize photobromination.

Two identical pumps (Ismatec peristaltic pump, Cole-Parmer SY-78017-00)were used to deliver the bromine/AlBr₃ and APS/BCM solutions to the CSTRusing feed lines of Teflon polymer (⅛″) and Viton fluoroelastomer(0.10″, Cole-Parmer, SY-07605-46). The operation was started by chargingthe CSTR with dry BCM (163.0 g) and cooling the contents of the reactorto −7° C. The bromine solution (2.29 g AlBr₃ in 525.0 g Br₂) and APSsolution (127.5 g APS in 187.3 g BCM, 40.5 wt % APS) feeds to thereactor were started at the same time and both were held constant forthe entire operation. The bromine feed rate was 2.87 ml/min and the APSfeed rate was 3.62 ml/min. The CSTR temperature varied from 0° C. to+10° C. during the operation. For the first 25 min, the overflow streamfrom the CSTR was directed to the waste quench pot (containing 635 g of4 wt % aqueous Na₃SO₃). After this point, the overflow stream wasdiverted to the main quench pot (containing 520 g of 4 wt % aqueousNa₃SO₃) to collect the steady state product. A small amount (10 g) ofbromine solution remained unused when the APS solution was depletedafter 60 min of operation. The weights of feed solutions used were:

1) 40.5 wt % APS in BCM, 314.8 g (224/n mol APS)

2) Br₂, 515 g (22 mol) 2.63 equiv.

3) 43 wt % AlBr₃ in Br₂ 2.25 g (0.0084 mol), 0.69 mol %

The average residence time for the reaction mass in the CSTR was 13 min.The organic phase in the main quench pot was diluted with BCM (288 g),and the lower organic phase was transferred to a 2-L separatory funnel.Two aqueous washes (900 g each) were used to remove residual acid andsalts.

The neutralized organic phase was pumped into 4-L of vigorously stirredhot (98° C.) water to obtain a slurry of white finely divided solid inwater. The slurry was suction filtered, and the solid was rinsed on thefilter with water (3×2L). The wet cake (89 g) was dried in a nitrogenpurged oven at 130° C. to a constant weight of 45.7 g. Analyticalresults are summarized in Table 2.

TABLE 2 APS BROMINATION RESULTS Example Ref D Ref E Ref F 4 BrominationProcess Batch Batch Batch Continuous Catalyst AlCl₃ AlCl₃ AlBr₃ AlBr₃AlX₃, mole % 0.75 1.43 1.41 0.69 Maximum reaction Temp (° C.) 0.00 +1 +3+10 Total reaction time or 75 76 35 13 ave. residence time (min) APSfeed concentration (wt %) 40.5 40.5 40.5 40.5 APS M_(n) 3400 3400 34003400 APS M_(w) 3800 3800 3800 3800 BrAPS Product Analyses Wt % Br (XRF)68.1 67.3 67.9 67.0 Thermal HBr, 320° C./15 min/N₂ (ppm) 119 90 180 104Thermal color, (320° C./15 min/N₂), 10 wt % in chlorobenzene L 95.4593.69 89.83 88.30 a -2.31 −3.32 −3.32 −2.62 b 14.80 21.86 30.74 31.67 ΔE15.70 22.99 32.58 33.88 Initial Color, 10 wt % in chlorobenzene L 99.6699.63 99.50 99.22 a −0.61 −0.71 −0.45 −0.64 b 2.47 2.75 2.64 3.61 ΔE2.63 2.92 2.81 3.82 DSC, T_(g) (° C.) 166.0 167.4 168.6 162.6 TGA 1% wtloss temp, N₂ (° C.) 352.8 355.4 354.1 349.2 BrAPS GPC M_(n) 13,00013,000 12,800 12,100 M_(w) 13,500 13,200 13,200 12,400 % Aromatic ringswith ortho-Br (NMR) 72.9 77.0 76.1 66.8 MFI (g/10 min, 220° C./2.16 kg)5.7 5.3 5.2 12.1

Reference Example G

This batch bromination was carried out using an anionic polystyrenehaving a number average molecular weight of 3200 and a weight averagemolecular weight of 3300. The bromine charge was increased from 2.70 to3.00 equivalents of bromine per aromatic ring. A 5.44 g (20.4 mmol)portion of aluminum bromide (Aldrich) was suspended in 199.8 g of dry(<15 ppm water) BCM in a 1-L, 5-necked, jacketed, glass reaction flaskcooled to −4° C. by a circulating glycol bath. The reaction flask havinga flush-mount Teflon polymer bottom valve was equipped with an overheadair stirrer and Teflon polymer banana-blade paddle, Friedrich'scondenser (glycol cooled), and thermowell. A constant flow of drynitrogen was maintained on the vent line from the condenser to assist inmoving exit gases from the flask to a caustic scrubber. A 500.0 gportion of a 30.0 wt % solution (150.0 g APS, 1.44/n mol) of the anionicpolystyrene in dry BCM was charged to a 500-mL graduated cylinder in adry box. The graduated cylinder was then set up to pump the APS solutionfrom the cylinder to a jacketed, glycol-cooled glass mixing tee mountedon the reaction flask. A solution of BCM (198.9 g) and bromine (690.4 g,4.320 moles, 3.00 equivalents) was charged to a second 500-mL graduatedcylinder and set up to pump the bromine to the same mixing tee as theAPS solution. A single pump motor (Ismatec peristaltic pump, Cole-ParmerSY-78017-00) having two pump heads was used to deliver equal volumes ofthe APS and bromine solutions to the mixing tee. Both streams werecooled separately by the mixer before combining at the bottom of theapparatus and dropping into the bromination flask. The reaction mixturewas protected from photo-initiated aliphatic bromination by turning offhood lights and wrapping the flask and mixing tee with Al foil. Bothfeeds were started at the same time and were both completed in 85 min Arinse of 100 g of dry BCM was used for the APS solution feed system toassure complete transfer of the polymer to the reaction flask whilenitrogen was flushed through the bromine feed system to givequantitative transfer of the bromine. The reaction temperature wasmaintained at −3° C. to 0° C. throughout the addition and subsequent 15min cook period (with nitrogen purge of the reactor overhead). Thecatalyst was deactivated by addition of 8.7 g of water. The organicphase was separated, and then washed with water, dilute caustic, andfinally water. The product was recovered from the organic phase byaddition to vigorously stirred hot (98° C.) water. The solvent distilledfrom the hot water leaving a slurry of the brominated polystyreneproduct in water. After suction filtering, the white solid was rinsedwith water (3×2L) and dried to a constant weight of 471.9 g (95% yield)in an oven (120° C.) under a constant nitrogen purge. Product analysesappear in Table 3.

Example 5

This continuous bromination was carried out as described in Example 1using 3.00 equivalents bromine. The APS used was the same as used inReference Example G. Product analyses are given in Table 3.

Reference Example H

This batch bromination was carried out using an anionic polystyrenehaving a number average molecular weight of 6200 and a weight averagemolecular weight of 6800 following the batch procedure described inReference Example A except for an increase in the bromine charge to 3.00equivalents. A 8.36 g (62.7 mmol) portion of aluminum chloride (Aldrich)was suspended in 799.1 g of dry (<15 ppm water) BCM in a 5-L, 5-necked,jacketed, glass reaction flask cooled to −3° C. by a circulating glycolbath. The reaction flask having a flush-mount Teflon polymer bottomvalve was equipped with an overhead air stirrer and Teflon polymerbanana-blade paddle, Friedrich's condenser (glycol cooled), andthermowell. A constant flow of dry nitrogen was maintained on the ventline from the condenser to assist in moving exit gases from the flask toa caustic scrubber. A 2093.7 g portion of a 20.0 wt % solution (418.7 gAPS, 4.02/n mol) of the anionic polystyrene in dry BCM was charged to a2-L flask in a dry box. The flask was then set up to pump the APSsolution from the flask to a jacketed, glycol-cooled glass mixing teemounted on the reaction flask. Bromine (1927.1 g, 12.06 moles, 3.00equivalents) was charged to a second 2-L flask and set up to pump thebromine to the same mixing tee as the APS solution. Both streams werecooled separately by the mixer before combining at the bottom of theapparatus and dropping into the bromination flask. The reaction mixturewas protected from photo-initiated aliphatic bromination by turning offhood lights and wrapping the flask and mixing tee with Al foil. Bothfeeds were started at the same time and were both completed in 196 min Arinse of 103 g of dry BCM was used for the APS solution feed system toassure complete transfer of the polymer to the reaction flask whilenitrogen was flushed through the bromine feed system to givequantitative transfer of the bromine. The reaction temperature wasmaintained at −3° C. to −1° C. throughout the addition and subsequent 15min cook period (with nitrogen purge of the reactor overhead). Thecatalyst was deactivated by addition of 72 g of water. A 73.8 g portionof 10 wt % aqueous sodium sulfite was then added to assure the removalof any residual bromine. The organic phase was separated, and thenwashed with water, dilute caustic, and water. The product was recoveredfrom the organic phase by addition to 6-L of vigorously stirred hot (98°C.) water in a 12-L pot. The solvent distilled from the hot waterleaving a slurry of the brominated polystyrene product in water. Aftersuction filtering, the white solid was rinsed with water (3×2L) anddried to a constant weight of 1337.1 g (97% yield) in an oven (150° C.)under a constant nitrogen purge. Product analyses appear in Table 3.

Example 6

This continuous bromination used the same anionic polystyrene used inReference Example H (number average molecular weight of 6200 and aweight average molecular weight of 6800) with only two feed streams tothe reactor. The bromine stream, containing the dissolved AlBr₃catalyst, and the APS solution in BCM were metered to the reactor usingtwo separate pumps An 80-mL capacity glass CSTR was used for thereaction. The reactor had an outer insulating vacuum jacket and an innerjacket for circulating glycol coolant. The vessel had two inlet ports onthe bottom for delivery of reagent solutions directly under the bottomturbine blade of the dual Teflon polymer turbine agitator (operated at400 rpm). An overflow port located just above the top turbine bladeallowed the reaction mixture to flow by gravity to a splitter that coulddirect the flow to the main product quench pot (5-L fully jacketed roundbottom flask with paddle stirrer) or a secondary waste quench pot (2-LErlenmeyer with magnetic stirrer). Exit gases from the CSTR passedoverhead through a Friedrich's condenser and into an aqueous causticscrubber with assistance from a constant nitrogen purge at the top ofthe condenser. During the bromination, the room and hood lights wereturned off to minimize photobromination.

Two identical pumps (Ismatec peristaltic pump, Cole-Parmer SY-780 17-00)were used to deliver the bromine/AlBr₃ and APS/BCM solutions to the CSTRusing feed lines of Teflon polymer (⅛″) and Viton fluoroelastomer(0.10″, Cole-Parmer, SY-07605-46). The operation was started by chargingthe CSTR with dry BCM (170.2 g) and cooling the contents of the reactorto −5° C. The bromine solution (18.01 g AlBr₃ in 2070.9 g Br₂) and APSsolution (450.58 g APS in 1802.3 g BCM, 20.0 wt % APS) feeds to thereactor were started at the same time and both were held constant forthe entire operation. The bromine feed rate was 2.93 ml/min and the APSfeed rate was 6.29 ml/min. The CSTR temperature varied from +3° C. to+7° C. during the operation. For the first 25 min, the overflow streamfrom the CSTR was directed to the waste quench pot (containing 468 g of5 wt % aqueous Na₂SO₃). After this point, the overflow stream wasdiverted to the main quench pot (containing 607 g of 7 wt % aqueousNa₂SO₃) to collect the steady state product. A small amount (62.9 g) ofbromine solution remained unused when the APS solution was depletedafter 221 min of operation. The weights of feed solutions used were:

1) 20.0 wt % APS in BCM, 2252.9 g (4.326/n mol APS)

2) Br₂, 2008.0 g (12.57 mol), 2.90 equiv.

3) 0.86 wt % AlBr₃ in Br₂, 17.46 g (0.0655 mol), 1.51 mol %

The average residence time for the reaction mass in the CSTR was 9 min.The organic phase in the main quench pot was transferred to a 2-Lseparatory funnel and then diluted with a BCM rinse (538 g) of thequench pot. The diluted organic phase was then washed with water, dilutecaustic, and finally water to remove residual acid and salts. Theneutralized organic phase was pumped into 6-L of vigorously stirred hot(98° C.) water to obtain a slurry of white finely divided solid inwater. The slurry was suction filtered, and the solid was rinsed on thefilter with water (3×2L). The wet cake (1702 g) was dried in a nitrogenpurged oven at 130° C. to a constant weight of 1219.3 g. Analyticalresults for the product are summarized in Table 3.

TABLE 3 BATCH AND CONTINUOUS BROMINATION REACTIONS FOR HIGH BROMINE BrPSPRODUCTS Example Ref G 5 Ref H 6 Bromination Process Batch ContinuousBatch Continuous Catalyst AlBr₃ AlBr₃ AlCl₃ AlBr₃ AlX₃, mole % 1.42 1.221.56 1.51 Maximum reaction Temp (° C.) 0 5 −1 7 Total reaction time or100 8 211 9 ave. residence time (min) APS feed concentration (wt %) 30.030.0 20.0 20.0 APS M_(n) 3200 3200 6100 6100 APS M_(w) 3300 3300 68006800 BrAPS Product Analyses Wt % Br (XRF) 70.3 69.9 70.1 69.4 ThermalHBr, 320° C./15 min/N₂ (ppm) 180 203 168 279 Thermal color, (320° C./15min/N₂), 10 wt % in chlorobenzene L 90.44 93.87 64.71 79.77 a −1.12−2.17 9.20 2.27 b 20.15 16.98 24.56 19.75 ΔE 22.49 18.26 44.35 28.76Initial Color, 10 wt % in chlorobenzene L 99.60 100.08 95.95 99.40 a−1.29 −0.47 −1.72 −0.84 b 4.19 1.69 11.29 3.64 ΔE 4.37 1.74 12.23 3.78DSC, T_(g) (° C.) 174.2 170.8 184.1 178.7 TGA 1% wt loss temp, N₂ (° C.)356.4 353.2 361.9 357.5 BrPS GPC M_(n) 11,000 12,900 21,400 23,800 M_(w)13,500 13,200 26,100 24,000 % Aromatic rings with ortho-Br (NMR) 90.784.3 85.3 78.8 MFI (g/10 min, 235° C./2.16 kg) 9.5 20.5 — — MFI (g/10min, 270° C./2.16 kg) — — 47.2 96.7

Table 4 summarizes the results of evaluation of glass filled nylon 6,6polymer blends containing various brominated flame retardants. The flameretardants used were Saytex® HP-3010 polymer (brominated polystyrene;Albemarle Corporation), Great Lakes PDBS80™, and samples of brominatedpolystyrenes of this invention from Examples 5 and 6, and samples ofbrominated polystyrenes Reference Examples G and H.

TABLE 4 Commercial BrPS Sample Commercial PDBS-80 Ex. 5 Ref. G Ex. 6Ref. H Parts Zytel ® 70G43L polymer (43% glass) 69.9 69.9 70.0 70.0 70.070.0 Parts Zytel 101 polymer 2.8 0.4 3.2 3.2 3.2 3.2 Parts Saytex ®3010, 68.0% Br 20.7 — — — — — Parts PDBS-80 ™ Fire Retardant, 61.1% Br —23.1 — — — — Parts BrPS 3300 Mw APS, 69.9% Br (continuous Br) — — 20.2 —— — Parts BrPS 3300 Mw APS, 70.3% Br (batch Br) — — — 20.2 — — PartsBrPS 6800 Mw APS, 69.4% Br (continuous Br) — — — — 20.2 — Parts BrPS6800 Mw APS. 70.1% Br (batch Br) — — — — — 20.2 Parts Antimony Trioxide6.2 6.2 6.2 6.2 6.2 6.2 Parts PTFE Teflon ® Polymer 6C 0.4 0.4 0.4 0.40.4 0.4 TESTING RESULTS UL-94 @ 1/16″ V-0 V-0 V-0 V-0 V-0 V-0 Burn TimeT1 25.5 18.9 21.0 24.6 37.3 16.6 Burn Time T1 + T2 30.4 23.0 25.4 30.145.5 24.8 Drip No No No No No No Melt Viscosity @ 250° C., 7300 1/sec;Pa* sec 49 45 — — 59 61 Melt Viscosity @ 265° C., 7300 1/sec; Pa* sec 4443 44 49 — — Notched Izod, ft-lb 1.5 1.3 1.8 1.8 1.7 1.6 Tensile @Break, kpsi 19.0 17.7 20.8 20.9 19.3 19.4 Elongation @ Break, % 2.9 2.73.3 3.6 3.2 3.3

From the foregoing it can be seen that this invention includes variousadditional embodiments such as for example:

I) A process of preparing a brominated styrenic polymer having increasedmelt flow properties measurable by use of ASTM Test Method D1238-00,which process comprises:

-   A) continuously forming reaction mixture from (i) a brominating    agent, (ii) a solution of styrenic polymer in a solvent, and (iii)    aluminum halide catalyst in which the halogen atoms are bromine or    chlorine with at least one such halogen atom being a bromine atom;-   B) causing said reaction mixture to continuously travel through and    exit from a reaction zone maintained at one or more temperatures in    the range of about −20 to about +20° C. (preferably in the range of    about 1 to about 10° C. and more preferably in the range of about 1    to about 5° C.), so that bromination of polymer occurs during at    least a portion of such travel;-   C) terminating bromination of polymer in the reaction mixture as or    after reaction mixture exits from the reaction zone; and-   D) continuously having the time between formation of reaction    mixture in A) and termination in C) in the range of 20 minutes or    less (preferably 10 minutes or less and more preferably 5 minutes or    less).

II) A process of preparing a brominated styrenic polymer product havingincreased melt flow properties at 235° C. and 2.16 kg or at 270° C. and2.16 kg in the melt flow index test, which process comprises:

-   A) continuously forming in, and continuously withdrawing from, a    reaction zone maintained at one or more temperatures in the range of    about −20° C. to about +20° C. (preferably in the range of about 1    to about 10° C. and more preferably in the range of about 1 to about    5° C.), a bromination reaction mixture formed from (i) a brominating    agent, (ii) a solution of styrenic polymer in a solvent, and (iii)    aluminum halide catalyst in which the halogen atoms are bromine or    chlorine with at least one such halogen atom being a bromine atom;-   B) providing reaction mixture in the reaction zone a residence time    for bromination of polymer to occur, such residence time being in    the range of no more than about 20 minutes (preferably 10 minutes or    less and more preferably 5 minutes or less) between formation and    withdrawal of reaction mixture; and-   C) terminating bromination of polymer in withdrawn reaction mixture    within 10 minutes (preferably within 5 minutes) after withdrawal,    the total time of B) and C) being no more than about 20 minutes.

III) A process as in I) or II) wherein bromination of polymer isterminated in C) by quenching withdrawn reaction mixture with aquenching composition comprising water in the liquid state.

As used anywhere herein, including the claims, the terms “continuous”and “continuously” denote that the operation referred to ordinarilyproceeds without interruption in time provided however that aninterruption is permissible if of a duration that does not disruptsteady-state conditions of that operation. If the interruption is of aduration that disrupts steady-state operation, a steady state conditionof operation should be achieved before resuming collection of theproduct.

It is to be understood that the components referred to by chemical nameor formula anywhere in the specification or claims hereof, whetherreferred to in the singular or plural, are identified as they existprior to coming into contact with another substance referred to bychemical name or chemical type (e.g., another component, a solvent, oretc.). It matters not what preliminary chemical changes, transformationsand/or reactions, if any, take place in the resulting mixture orsolution as such changes, transformations, and/or reactions are thenatural result of bringing the specified components together under theconditions called for pursuant to this disclosure. Thus the componentsare identified as ingredients to be brought together in connection withperforming a desired operation or in forming a desired composition. Eventhough the claims hereinafter may refer to substances, components and/oringredients in the present tense (“comprises”, “is”, etc.), thereference is to the substance, component or ingredient as it existed atthe time just before it was first contacted, blended or mixed with oneor more other substances, components and/or ingredients in accordancewith the present disclosure. The fact that a substance, component oringredient may have lost its original identity through a chemicalreaction or transformation during the course of contacting, blending ormixing operations, if conducted in accordance with this disclosure andwith the application of common sense and the ordinary skill of achemist, is thus wholly immaterial for an accurate understanding andappreciation of the true meaning and substance of this disclosure andthe claims thereof.

Each and every patent or publication referred to in any portion of thisspecification is incorporated in toto into this disclosure by reference,as if fully set forth herein.

This invention is susceptible to considerable variation in its practice.Therefore the foregoing description is not intended to limit, and shouldnot be construed as limiting, the invention to the particularexemplifications presented hereinabove. Rather, what is intended to becovered is as set forth in the ensuing claims and the equivalentsthereof permitted as a matter of law.

1. Brominated anionic styrenic polymer having (i) a bromine content ofat least about 66 wt %, (ii) a GPC weight average molecular weight inthe range of about 8000 to about 50,000, and (iii) a higher melt flowindex as compared to previously-known comparable brominated anionicstyrenic polymers, as measured using ASTM Test Method D1238-00. 2.Brominated anionic styrenic polymer as in claim 1 wherein said GPCweight average molecular weight is in the range of about 10,000 to about30,000.
 3. Brominated anionic styrenic polymer as in claim 1 whereinsaid GPC weight average molecular weight is in the range of about 10,000to about 20,000.
 4. Brominated anionic styrenic polymer as in claim 1wherein said polymer has a thermal stability in the 320° C. ThermalStability Test of 300 ppm of HBr or less.
 5. Brominated anionic styrenicpolymer as in claim 1 wherein said polymer has a thermal stability inthe 320° C. Thermal Stability Test of 125 ppm of HBr or less. 6.Brominated anionic styrenic polymer as in claim 1 wherein said polymerhas an initial Hunter Solution ΔE Color Value of 5 or less. 7.Brominated anionic styrenic polymer as in claim 1 wherein said polymerhas an initial Hunter Solution ΔE Color Value of 3 or less. 8.Brominated anionic styrenic polymer as in claim 1 wherein said polymerhas a thermal stability in the 320° C. Thermal Stability Test of 300 ppmof HBr or less, wherein said polymer has a GPC weight average molecularweight in the range of about 10,000 to about 30,000, and wherein saidpolymer has an initial Hunter Solution ΔE Color Value of 5 or less. 9.Brominated anionic styrenic polymer as in claim 1 wherein said polymerhas a thermal stability in the 320° C. Thermal Stability Test of 125 ppmof HBr or less, wherein said polymer has a GPC weight average molecularweight in the range of about 10,000 to about 20,000, and wherein saidpolymer has an initial Hunter Solution ΔE Color Value of 3 or less. 10.Brominated anionic styrenic polymer as in claim 1 wherein said polymerhas a bromine content in the range of about 67 to about 70 wt %. 11.Brominated anionic styrenic polymer as in claim 10 wherein said polymeris brominated anionic polystyrene.
 12. Brominated anionic styrenicpolymer wherein said polymer has a bromine content of at least about 66wt % and wherein said polymer is one in which the percentage of aromaticrings having ortho bromine atoms thereon as measured by proton NMR isless than the percentage of the aromatic rings having ortho bromineatoms thereon in previously-known comparable brominated anionic styrenicpolymers.
 13. Brominated anionic styrenic polymer as in claim 12 whereinthe percentage of aromatic rings having ortho bromine atoms thereon isat least 5% less than the percentage of aromatic rings having orthobromine atoms thereon in said previously-known comparable brominatedanionic styrenic polymers.
 14. Brominated anionic styrenic polymer as inclaim 12 wherein said polymer has a bromine content in the range ofabout 67 to about 69 wt % and wherein the percentage of aromatic ringshaving ortho bromine atoms thereon is at least 10% less than thepercentage of aromatic rings having ortho bromine atoms thereon in saidpreviously-known comparable brominated anionic styrenic polymers. 15.Brominated anionic styrenic polymer as in claim 12 wherein said polymerhas a thermal stability in the 320° C. Thermal Stability Test of 300 ppmof HBr or less.
 16. Brominated anionic styrenic polymer as in claim 12wherein said polymer has an initial ΔE Color Value of 5 or less. 17.Brominated anionic styrenic polymer as in claim 12 wherein thepercentage of aromatic rings having ortho bromine atoms thereon is atleast 5% less than the percentage of aromatic rings having ortho bromineatoms thereon in said previously-known comparable brominated anionicstyrenic polymers, and wherein said polymer has a thermal stability inthe 320° C. Thermal Stability Test of 300 ppm of HBr or less. 18.Brominated anionic styrenic polymer as in claim 12 wherein said polymerhas a thermal stability in the 320° C. Thermal Stability Test of 300 ppmof HBr or less and wherein said polymer has an initial Hunter SolutionΔE Color Value of 5 or less.
 19. Brominated anionic styrenic polymer asin claim 13 wherein said polymer has a bromine content in the range ofabout 67 to about 70 wt %.
 20. Brominated anionic styrenic polymer as inclaim 13 wherein said polymer is brominated anionic polystyrene. 21.Brominated anionic styrenic polymer as in claim 13 wherein said polymerhas a GPC weight average molecular weight in the range of about 8,000 toabout 50,000.
 22. A flame retardant composition which comprises a blendof at least one thermoplastic polymer and a flame retardant amount of atleast one brominated anionic styrenic polymer as in claim
 12. 23.Brominated anionic styrenic polymer wherein said polymer has an initialHunter Solution ΔE value in the range of up to 1.50.
 24. Brominatedanionic styrenic polymer as in claim 23 wherein said initial ΔE value isin the range of 0.15 to 1.40.
 25. Brominated anionic styrenic polymer asin claim 23 wherein said initial ΔE value is in the range of 0.18 to1.32.
 26. Brominated anionic styrenic polymer as in claim 25 whereinsaid polymer additionally has (1) a GPC weight average molecular weightin the range of about 8,000 to about 50,000, or (2) a thermal stabilityin the 320° C. Thermal Stability Test of 300 ppm of HBr or less, or (3)a bromine content of at least about 66 wt %, or (4) a combination of anytwo, or all three, of (1), (2), (3).
 27. Brominated anionic styrenicpolymer as in claim 26 wherein said polymer has a combination of allthree of (1), (2), (3), and wherein the GPC weight average molecularweight of (1) is in the range of about 10,000 to about 30,000, whereinthe thermal stability in the 320° C. Thermal Stability Test of (2) is200 ppm of HBr or less, and wherein the bromine content of (3) is in therange of about 67-70 wt %.
 28. Brominated anionic styrenic polymer as inclaim 26 wherein said polymer is brominated anionic polystyrene. 29.Brominated anionic styrenic polymer as in claim 27 wherein said polymeris brominated anionic polystyrene.
 30. A flame retardant compositionwhich comprises a blend of at least one thermoplastic polymer and aflame retardant amount of at least one brominated anionic styrenicpolymer as in claim 1.